Controllers in motor vehicles can communicate via various bus systems, such as CAN, MOST, FlexRay or LIN bus systems. The cited bus systems differ in terms of their properties, such as a data rate for data to be transmitted, connector and cable types, number of controllers that can be connected to the bus system, maximum admissible cable length, etc. Power can be supplied to the controllers from an onboard power supply system, usually via what are known as terminals. In this case, controllers can be supplied with power from an onboard power supply system only when required or constantly.
In the case of constantly supplied controllers, there is the problem that such controllers are a constant load on the energy stores in the motor vehicle, particularly the onboard power supply system battery, which can result in the onboard power supply system battery being drained completely. Methods for network management have therefore been developed which can put controllers into a switched-off state or a sleep state when required, from which state they can then be awoken. Switching off or putting controllers into a sleep state allows a reduction in energy consumption by the controllers, which relieves the load on the onboard power supply system battery.
With the aim of further energy saving, methods are currently being developed for operating networks in what is known as a partial network mode. In this case, it is meant to be possible to specifically connect and disconnect selected controllers, and hence to allow them to communicate with one another only as required, even during a driving mode of the motor vehicle. However, implementing such a partial network mode requires complex logic to be integrated into the transceiver chips and controllers of the respective bus system. In addition, suitable control is necessary for coordinating the network state. This increases the system complexity, which is high anyway, and creates an increased potential for error.
In contrast to CAN, FlexRay and LIN bus systems, Ethernet allows DC-free communication. In bus systems implemented at Ethernet, it is therefore possible for a communication signal, usually an AC voltage signal, to be modulated onto a DC voltage without needing to fear losses in a quality of the communication. DE 10 2008 030 222 A1 discloses a controller for communicating with a differential bus system, wherein the controller comprises a coupling unit for supplying and/or detecting a signal, the coupling unit using a common potential with a further unit connected to the bus system.
When controllers are supplied with power from an onboard power supply system, there may be a need to transform a voltage level of the onboard power supply system voltage to a voltage level of an operating voltage for the respective controller. For such a transformation, it is possible to use what are known as switched-mode regulators and what are known as in-phase regulators, inter alia. In a switched-mode regulator, an input voltage for the switched-mode regulator is periodically switched on and off and passed to a storage element. Depending on the ratio of switched-on to switched-off time, a particular average voltage is established at the output of the switched-mode regulator or the storage element. An advantage in this context is low power loss, but disadvantages are a high level of circuit complexity and EMC disturbances as a result of fast switching operations.
By contrast, in-phase regulators afford the advantage of a lower-disturbance output voltage, but have poorer efficiency than switched-mode regulators on account of relatively great heat loss. However, there is the problem that when the controllers are supplied with power from the onboard power supply system, it is necessary for each controller to have at least one of the regulators described above associated with it.